Patient-specific white blood cell malignancy vaccine from membrane-proteoliposomes

ABSTRACT

Membrane-proteoliposome structures (MPs) are useful in preparing patient-specific vaccines against specific white blood cell (WBC) malignancies. The inventive MPs typically contain a membrane component derived from a specific WBC. Other useful components include immunostimulators and exogenous lipids. The resulting vaccines are both patient- and malignancy-specific.

BACKGROUND OF THE INVENTION

[0001] The present invention is directed to the production of novelcompositions, useful as vaccines for treating white blood cell (WBC)malignancies. The invention relates to a liposomal, patient-specificvaccine comprised of WBC membranes that may be formulated by addingother lipids and/or immunostimulators, thereby forming a novelmembrane-proteoliposome (MP) structure.

[0002] Known vaccines typically utilize either purified antigen orattenuated pathogen as the immunogen. However, attenuated vaccines canactually cause the infection against which a person is being immunized.On the other hand, purified antigens may not induce a long-term immuneresponse and sometimes induce no response at all. In contrast to theshort-term immune response obtained by direct immunization with certainantigens, presentation of the antigen in the presence of liposomes caninduce a long-term response which is essential for any effectivevaccine.

[0003] Although typically formed from purified or partially purifiedlipids, liposomes may also be formed, at least in part, from cellmembranes of malignant cells which contain potential antigens. Due tothe presence of membrane associated antigens, these membrane-derivedpreparations may be used as malignancy-specific vaccines. Indeed, sometypes of membrane-derived preparations have been used as tumor specificantigens (TSA) to treat melanomas and murine SL2 lymphosarcoma. SeeGershman et al., Vaccine Res. 3:83-92 (1994); Bergers et al., J. Confr.Rel. 29:317-27 (1994); Bergers et al., J. Liposome Res. 6:339-35 (1996).In these cases, the production of vaccine suffered from seriousdisadvantages. Namely, they required pooling culture adapted cells toachieve large amounts of the desired cell populations, use of wholeγ-irradiated tumor cells, detergent solubilization or butanol for crudeextraction of tumor-associated antigens (TAA). See Gershman et al.(1994), supra; Abbas, et al., CELLULAR AND MOLECULAR IMMUNOLOGY,pp.372-73 (W. B. Saunders Company, Philadelphia 1994); Bergers et al.(1994), supra; LeGrue et al., J. Natl. Cancer Inst. 65:191-96 (1980).This approach, moreover, is not patient-specific.

[0004] The art is also aware of some vaccines directed to certain B cellmalignancies. Typically, however, attempts at producing vaccines forB-cell lymphoma have relied on the costly and time consuming hybridomatechnology. These methods depend on generating a hybridoma able toproduce the tumor-specific immunoglobulin (Ig) in enough quantity to bethen used as a vaccine. Kwak et al., Blood 76:2411-17 (1990); Kwak etal., N. Engl. J. Med. 327:1209-15 (1992). Known B-cell lymphoma vaccinesemploy Ig idiotype (Id) to generate anti-idiotype antibodies to B-cells.Levy et al., PCT/US94/08601 (Feb. 23, 1995); Levy et al., U.S. Pat. No.4,816,249 (1989). Similarly, known melanoma vaccines involved harvestingcell surface antigens which are shed during culturing. Bystryn, U.S.Pat. No. 5,635,188 (1997); Bystryn, U.S. Pat. No. 5,194,384 (1993);Bystryn, U.S. Pat. No. 5,030,621 (1991).

[0005] There is, therefore, an unmet need in the art for improvedliposome-based vaccines. A particular need exists for improved vaccinesagainst white blood cell malignancies.

SUMMARY OF THE INVENTION

[0006] Accordingly, it is an object of the invention to provide novelvaccine compositions that overcome the above-identified and otherdeficiencies in the art. According to this object of the invention,membrane-proteoliposomes (MPs) are provided which aremalignancy-specific, patient-specific and are easily prepared. Thus, inone embodiment, MPs are provided which comprise the cell membrane of awhite blood cell malignancy, at least one immunostimulator and at leastone lipid, where the lipid may be added in the form of lipid powder, orpreformed liposomes. Another embodiment of the invention provides novelvaccine formulations which comprise an MP comprising the cell membraneof a white blood cell and may include at least one immunostimulator.

[0007] It is yet another object of the invention to provide methods forpreparing MPs and vaccines which also overcome the deficiencies in theart. According to this object of the invention, methods are disclosedthat do not rely on harvesting the vaccine antigen, hybridoma productionor other intermediate steps. The inventive methods comprise formulatinga vaccine directly from isolated antigen-containing membranes frompatients' own white blood cells (WBCs), thus rendering them highlyeffective and patient-specific.

BRIEF DESCRIPTION OF THE DRAWING

[0008]FIG. 1 exhibits the survival results after mice were vaccinatedwith the MP formulation described in Example 5.

[0009]FIG. 2 demonstrates the patching seen in membrane-proteoliposomes,where the patches consist of DMPC-rich and WBC membrane-rich domains(see arrows).

DETAILED DESCRIPTION

[0010] Introduction

[0011] The instant invention provides membrane-proteoliposome structures(MPs) that are useful in formulating patient-specific vaccines fortreating white blood cell (WBC) malignancies.

[0012] The inventors previously described a proteoliposomal vaccine madeof antigen idiotype (Id) and interleukin-2 (IL-2) proteins within aliposomal structure (Popescu, et al., PCT/US97/02351). In contrast tothat earlier work, a novel liposomal structure is disclosed herein,called a membrane-proteoliposome (MP), which usually comprisesphospholipid, integral membrane from a malignant WBC and a potentimmunostimulator. The present invention is based in part on thediscovery that membranes from WBC malignancies can be fused with othercomponents to form an effective vaccine against the malignancy.

[0013] All WBCs, including polymorphonuclear cells (PMN), monocytes andT- or B-lymphocytes, are subject to malignant transformation leading toa spectrum of diseases. For example, B-cell malignancy includesnon-Hodgkin's lymphomas, chronic lymphocytic leukemia and multiplemyeloma. The present invention has relevance in treating or preventingmany such malignancies.

[0014] In preparing the inventive vaccines, WBC's can be obtaineddirectly from the patient to isolate the intact membranes, rich intumor-specific antigens (TSA) and tumor-associated antigens (TAA). Ingeneral cells will be enucleated and their plasma membranes separatedfrom other components (e.g., mitochondria, lysosomes). The plasmamembranes typically are washed to remove cellular contaminates, whichmay include cytoskeletal structures, and the separation material. Theplasma membrane suspensions may then be exposed to mechanical sizereduction, for example, by extrusion, homogenization or other shearingmethods. This will allow for filtration through a sterilizing filter.The WBC membranes may also be detergent solubilized, reconstituted withlipids of choice then size reduced. In lieu of mechanical size reductionmethods, the isolated membranes may be sterilized by, for example,γ-irradiation.

[0015] The isolated malignant cell membranes, alone or in combinationwith added lipids, can then be used to entrap an immunomodulator. Theextent of entrapment of immunomodulator, immunogenicity and efficacy ofthe MP as a vaccine can be modulated by the nature of the constitutivelipids. A thus optimized MP formulation may then be used to vaccinatethe patient against his/her specific WBC malignancy.

[0016] The present invention is particularly useful in vaccinatingagainst non-Hodgkin's lymphomas. These lymphomas are characterized bythe expression of monotypic immunoglobulin (Ig) which can serve as atumor-specific antigen. In addition, these cells express surfacemolecules involved in antigen presentation, such class I and class IIMHC molecules, and costimulation, such as adhesion proteins and B7.1 andB7.2 (CD80 and CD86). In particular, the presence of a class I MHCmolecule in the inventive formulation will potentially enhance thecytotoxic immune response against the tumor. These characteristics makethe B-cell lymphoma plasma membrane an attractive candidate that can beused as a potentially strong immunogenic tool in active specificimmunotherapy.

[0017] The present invention provides a proteoliposomal,patient-specific vaccine for WBC malignancies that, in one embodiment,is produced by entrapping a potent immunomodulator together withmalignant white blood cell membranes. The resultingmembrane-proteoliposome can be either (1) a cell-derived membranepatched with at least one added membrane-forming lipid or (2) a lipidmembrane (e.g., a liposome) patched with cell-derived membrane. By“patched” is meant that the resulting MP is non-homogenous with respectto the component lipid sources. Thus, contiguous portions of the MP willbe essentially WBC membrane-derived, while others will be derivedessentially from the added membrane-forming lipids. In three examplesbelow, MP formulations are described which contain membrane from a mouseB-cell lymphoma (38C13), and which were used as effective vaccines in amouse model of non-Hodgkin's B-cell lymphoma.

[0018] Vaccine Compositions of the Invention

[0019] The vaccine compositions of the invention typically comprise atleast one membrane component of a malignant white blood cell. Importantmembrane components specifically include components involved inimmunity. Components involved in immunity can include anymacromolecules, such as proteins, lipids and carbohydrates, which arenormally an integral part of, or simply associated with, the cellmembrane. Other organic and inorganic substances which are similarlyassociated with the cell membrane also are included. Some preferredcomponents involved in immunity include tumor-specific antigens (TSA),tumor associated antigens (TAA), major histocompatability (MHC) antigens(class I and class II molecules) and costimulatory molecules.

[0020] Costimulatory molecules are second signal immunostimulatorsassociated with T cell activation. Costimulatory molecules typically arecell surface molecules which act in conjunction with primary immunesignals, i.e., antigen presented by MHC molecules, to generate an immuneresponse. Thus, acting in concert, primary and secondary signalmolecules facilitate antigen presentation by antigen presenting cells(APC) to T cells. Examples of costimulatory molecules include cellularadhesion molecules and CD-40. Specific preferred costimulatory moleculesinclude B7.1 and B7.2.

[0021] Preferably, the membrane component takes the form of an isolatedplasma membrane (in whole or in part). The isolated plasma membranepreferably is constituted of lipid which is membrane-forming. Thus, allcomponents normally integral to or associated with the cell plasmamembrane, including components involved in immunity, typically arepresent. This preferred membrane component will usually be isolated froma patient sought to be vaccinated. Thus, the resultant vaccinecomprising this membrane component will be patient-specific and specificfor the WBC malignancy from which the membrane component is isolated. Itis envisioned that a vaccine formulated with a membrane component fromone patient will be useful in vaccinating another patient, given similarantigenic determinants. Of course, it is also possible, due tocross-reactivity or common antigenic determinants, that the vaccine forone malignancy will prove useful in vaccinating against anothermalignancy. Thus, as used herein, “patient-specific” refers to the factthat the vaccine is derived from a particular patient (it thus will beuseful in treating that same patient), not that it is useful only totreat the patient or the specific malignancy from which it is derived.Although the patient will normally be human, non-human animals may alsobe patients.

[0022] The inventive vaccine compositions can be made specific for anywhite blood cell malignancy. The clinician will be familiar with thevarious types of white blood cells and their malignancies.Representative white blood cells include polymorphonuclear cells (PMNs),monocytes, T-lymphocytes and B-lymphocytes. Some representative whiteblood cell malignancies include lymphomas, leukemias, and myelomas.Other white blood cell malignancies are known in the art. Furtherexamples of WBC malignancies are found in McCance et al.,PATHOPHYSIOLOGY: THE BIOLOGIC BASIS OF DISEASE IN ADULTS AND CHILDREN,chapters 24 and 25, pp. 800-855 (The C.V. Mosby Company 1990), which arehereby incorporated by reference.

[0023] Some preferred vaccine compositions further comprise at least oneimmunostimulator. Immunostimulators specifically include any substancethat can be used to modulate the immune response. Especially usefulimmunostimulators are those which can be used to stimulate the specificimmune response to components involved in immunity. Exemplary classes ofsuch useful immunostimulators include: lymphokines, such as IL-2, IL-4and IL-6; interferons, such as IFN-γ and IFN-α; other cytokines, such asGM-CSF and M-CSF; and adjuvants, such as Lipid A, monophosphoryl lipid A(MPL), lipid A, or muramyl dipeptide (MDP). Immunostimulators may beused alone or in any combination with one another. Some compositionscomprise at least two immunostimulators, such as IL-2 and MPL or MDP,and other combinations of cytokines with adjuvants.

[0024] Other preferred vaccine compositions comprise lipids other thanthose present in the cell membrane component (i.e., from an exogenoussource). These “exogenous” lipids may be from natural or syntheticsources. Preferred lipids include phospholipids, glycolipids, andespecially saturated phospholipids. Saturated phospholipids include1,2-dimyristoylphosphatidylcholine (DMPC),1,2-dipalmitoylphosphatidylcholine (DPPC),1,2-dimyristoylphosphatidylglycerol (DMPG). Other useful lipids includecholesterol and derivatives thereof. Of course combinations of these andother lipids are also useful.

[0025] Methods for Preparing the Inventive Vaccines

[0026] Preparing an inventive vaccine involves first isolating WBCmembrane components, free of other cellular components. One such exampleis provided below as Example 4. According to a preferred embodiment,isolated membranes typically are combined with other lipids and/orimmunostimulators to form MPs. There are many liposome-forming methodsknown in the art and any of these standard methods may be employed inpreparing the present MP.

[0027] In one exemplary method MPs can be prepared containing IL-2 as animmunostimulator. The IL-2 is mixed with the WBC membranes and entrappedby freeze/thawing from −70° C. to 37° C., followed by brief vortexingand short bath sonication (30 seconds). The preparation can include theaddition of a suitable lipid powder at 50 to 300 mg/mL (final). Thus,using this method MPs can be formed independent of exogenous lipids orfrom WBC membrane components mixed with exogenous lipids.

[0028] MPs can also be prepared containing only WBC membrane components,which may be fused with preexisting liposomes which comprise exogenouslipids. A WBC membrane suspension is lyophilized then hydrated with asuitable liquid, for example, water, normal saline solution (NSS) or asuitable buffer. The hydration liquid may contain an immunomodulator.Thus, MPs comprising WBC membrane components are formed. In addition,pre-formed multilamellar vesicles (MLVs), composed of suitable exogenousliposome-competent lipids, may be mixed with the WBC membrane suspensionprior to lyophilization. The MLVs may contain a pre-incorporatedimmunomodulator, in which case the lyophilized preparation is hydratedwith a suitable liquid, which may contain at least one immunomodulator.Thus, in any method for preparing MPs, any combination of multipleimmunostimulators may be incorporated at any suitable point in theprocess.

[0029] In another method, the WBC membrane suspension is size reduced byextrusion, homogenization or other shearing methods to form smallunilamellar vesicles (SUVs). The SUVs are then lyophilized and hydratedwith a suitable liquid, optionally containing an immunomodulator. SUVsprepared from exogenous lipids also may be added prior to thelyophilization step. In addition, the immunomodulator may be mixed withthe SUV's prior to lyophilization. In any event, whenever thelyophilized preparation is hydrated, the liquid may contain animmunomodulator.

[0030] In yet another method, a WBC membrane suspension is added to MLVscomprising exogenous lipids. The resulting mixture is lyophilized andhydrated with water, NSS or buffer followed by size reduction(extrusion, homogenization or other shearing methods) to form SUV's. Animmunomodulator may be added and the mixture is allowed to fuseovernight.

[0031] Another method involves adding a WBC membrane suspension to MLVscomprising exogenous lipids. The mixture is lyophilized and hydratedwith a suitable liquid. The resulting suspension is size reduced byextrusion, homogenization or other shearing methods to form SUVs. TheSUVs are lyophilized and hydrated with a suitable liquid, optionallycontaining an immunomodulator.

[0032] Also, the WBC membrane suspension may be size reduced byextrusion, homogenization or other shearing methods to form SUVs. Animmunomodulator is added to the SUVs and the mixture is then allowed tofuse overnight.

[0033] Vaccines may also be formulated with a pharmaceuticallyacceptable excipient. Such excipients are well known in the art, buttypically should be physiologically tolerable and inert or enhancingwith respect to the vaccine properties of the inventive compositions.When using an excipient, it may be added at any point in formulating thevaccine or it may be admixed with the completed vaccine composition.

[0034] Vaccines may be formulated for multiple routes of administration.Specifically preferred routes include intramuscular, percutaneous,subcutaneous, or intradermal injection, aerosol, oral or by acombination of these routes, at one time, or in a plurality of unitdosages. Administration of vaccines is well known and ultimately willdepend upon the particular formulation and the judgement of theattending physician.

[0035] Vaccine formulations can be maintained as a suspension, or theymay be lyophilized and hydrated later to generate a useable vaccine.

EXAMPLES Example 1

[0036] Isolation of Plasma Cell Membranes

[0037] This example demonstrates a method for isolating WBC plasmamembranes. Frozen (−70° C.) 38C13 murine B-lymphoma cells werequick-thawed at 37° C., suspended at 2× 10⁸ cells/mL in homogenizationbuffer (HB). The composition of HB was 0.25 M sucrose, 10 mM Tris/HCl, 1mM MgCl₂, 1 mM KCl, phenylmethylsulfonyl fluoride (PMSF, 2 mM, final),trypsin-chymotrypsin inhibitor (200 μg/mL, final), DNase (10 μg/mL,final) and RNase (10 μg/mL, final), pH 7.3. The 38C13 cells wereenucleated in a hand-held Dounce homogenizer (20-30 passes while onice). The slurry was spun at 500×g (10 minutes, 4° C.) and thesupernatant collected. The pellet was resuspended in HB and thehomogenization and centrifugation steps repeated until the pellet, asjudged by light microscopy, was essentially free of intact cells (˜95%nuclei only). The pooled supernatants were layered on a discontinuoussucrose gradient (p=1.11, 1.18 and 1.25 g/mL) and spun at 28K×g (30minutes, 4° C.). The plasma membrane-rich region was collected(p=1.11/1.18 interface), diluted two-fold with NSS and spun 28K×g (1hour, 4° C.). The pellet was again diluted two-fold with the NSS andrespun as above. The washed membranes were resuspended in a minimalamount of NSS and stored at 4° C.

Example 2

[0038] Preparation of Membrane Proteoliposomes

[0039] This example demonstrates a method of formulating a vaccine fromisolated WBC membranes. Experimental vaccine MB-RM-1A was formulated asfollows: DMPC powder (1 g), 4 mL of the isolated 38C13 membranes (225μg/mL IgM) in NSS and 160 ul of IL-2 (1.25×10⁸ IU/mL) were placed in a 5mL sterile glass vial, immediately vortexed, heated to 37° C. for 15minutes in a water bath, then sonicated at 37° C. for 30 seconds in abath sonicator. This suspension was subjected to three freeze/thawcycles as follows:

[0040] 1) Freezing at −70° C. (dry ice/methanol bath) for 15 minutes

[0041] 2) Thawing at 37° C. (water bath) for 15 minutes

[0042] 3) Vortexing briefly

[0043] 4) Sonicating for 30 seconds in a bath sonicator at 37° C.

[0044] The preparation was adjusted to a total volume of 5 mL with NSSand stored at −70° C.

Example 3

[0045] Comparative Vaccine Effectiveness

[0046] This example demonstrates the effectiveness of exemplary vaccinesproduced according to the invention, and particularly the freeze/thawmethod of Example 2. The results presented below, and depicted in FIG.1, show that the vaccinated mice survived a lethal B-cell lymphomachallenge.

[0047] As seen in the following Table, the exemplary freeze-thaw MPvaccine, MB-RM-1A, effectively protected 85% of the mice challenged witha lethal dose of 38C13 lymphoma cells. By comparison, as summarizedbelow, the survival associated with control vaccine formulations waslower. TABLE Vaccine Description Percent Survival MB-RM-1A MP vaccine 854C5-Id Non-specific antigen 0 38C13-Id Control vaccine 10 38C13-Id-KLHControl vaccine 40 OV XIV-2 Liposomal vaccine 50

[0048] The foregoing sample designations correspond to the following:4C5-Id is a non-specific antigen control; 38C13-Id is a vaccineconsisting of soluble 38C13 immunoglobulin; 38C13-Id-KLH is a vaccineconsisting of a conjugate between keyhole limpet hemocyanin and soluble38C13; OV XIV-2 is a liposomal vaccine containing soluble 38C13-Id andIL-2. See Kwak et al. J. Immunol. 160: 3637-3641 (1998); Popescu et al.PCT/US97/02351.

Example 4

[0049] Comparative Vaccine Effectiveness

[0050] Preparation. A frozen (−70° C.) pellet of 38C13 cells was quicklythawed at 37° C. in a water bath, then placed on ice. All subsequenttreatments, unless otherwise specified were carried out on ice at 4° C.The pellet was washed with (5) volumes of ice cold PBS at 1K×g×10minutes. The pellet was resuspended in ice-cold NSS containing 2 mMphenylmethylsulfonyl fluoride (PMSF), and 100 μg/mL each of DNAse andRNAse. The cells were enucleated by emulsification through a 22 gaugeneedle (50 passes) and by using a hand held Dounce homogenizer (50passes). The suspension was spun to pellet the nuclei at 330×g×10minutes and the supernatant was layered on a Nycodenz gradient (p=1.22)and spun at 60K×g×1 hour. WBC plasma membranes were collected at thewater/Nycodenz interface and washed with (7) volumes of NSS at 60K×g×30minutes. The pelleted membranes were resuspended in NSS. A portion ofthese membranes was used to formulate MCFC9803 using the freeze/thawmethod as described in Example 2. The rest of the washed cell membraneswere homogenized at ˜22K psi (15-20 passes) and used to formulatepreparations MCFA9803 and MCFB9803. The following describes theexperimental design of formulations MCFA9803, MCFB9803 and MCFC9803:

[0051] MCFA9803:

[0052] a) Homogenized WBC membranes were added to DMPC SUVs and IL-2.

[0053] b) The mixture was allowed to coalesce into MLVs by overnightincubation at 19° C. (Boni et al., PCT Application based on U.S. Ser.No. 60/060,606 “Multilamellar Coalescence Vesicles (MLCV) ContainingBiologically Active Compounds”).

[0054] MCFB9803:

[0055] a) Homogenized WBC membranes were added to DMPC SUVs andlyophilized.

[0056] b) MLVs were formed upon reconstitution with buffer containingIL-2.

[0057] MCFC9803:

[0058] a) DMPC (powder) and IL-2 were added to a suspension of WBC cellmembranes.

[0059] b) MLVs were formed by the freeze-thaw method detailed in Example2.

[0060] Survival data. FIG. 1 shows the effectiveness of MP vaccinesproduced according to the invention, and particularly shows survivaldata after formulation using three different methods for preparation.The results show that the vaccinated mice survived a lethal B-celllymphoma challenge. The exemplary MP vaccines, MCFA9803 and MCFC9803,effectively protected 78% ({fraction (7/9)}) and 90% ({fraction(9/10)}), respectively, of the mice challenged with a lethal dose of38C13 lymphoma cells. Addition of IL-2 after lyophilization and duringreconstitution was less effective (MCFB9803, 20% survival). However, allthe formulations offer some protection in this model of lymphoma.

Example 5

[0061] Proteoliposome Characterization

[0062] This example demonstrates one alternate method of formulating avaccine from isolated WBC membranes. SUVs (0.5 mL at 200 mg/mL) preparedfrom DMPC, WBC membranes (0.5 mL) and IL-2 (19 μl at 1.07×10⁸ IU/mL) arecombined and the mixture is lyophilized. Upon reconstitution with 0.5 mLdistilled water 59% of the IL-2 is recovered of which 100% isincorporated in the membrane-proteoliposomes and 84% of the IgM isrecovered of which 80% is incorporated in the membrane-proteoliposomes.The mean membrane-proteoliposome size is 2.8 microns. Freeze-fractureelectron microscopy shown in FIG. 2 reveals membrane-proteoliposomeswith the characteristic ripple phase DMPC liposomes mixed with WBCmembranes containing intramembranous particles. The two distinct domainsin one membrane-proteoliposome define the “patching” of WBC membraneswith DMPC lipids.

[0063] The foregoing discussion and examples are presented merely forillustrative purposes and are not meant to be limiting. Thus, oneskilled in the art will readily recognize additional embodiments withinthe scope of the invention that are not specifically exemplified.

What is claimed is:
 1. A patient-specific vaccine for treating whiteblood cell malignancy, comprising a membrane-proteoliposome (MP)containing plasma membrane from a malignant white blood cell.
 2. Avaccine according to claim 1 , wherein said malignant white blood cellis a lymphoma cell.
 3. A vaccine according to claim 1 , wherein saidmalignant white blood cell is a leukemia cell.
 4. A vaccine according toclaim 1 , wherein said malignant white blood cell is a myeloma cell. 5.A membrane-proteoliposome (MP), comprising integral membrane from amalignant white blood cell, at least one immunostimulator and anexogenous lipid.
 6. An MP according to claim 5 , wherein said membranecontains at least one membrane component involved in immunity.
 7. An MPaccording to claim 5 , comprising at least two immunostimulators.
 8. AnMP according to claim 6 , wherein said component is selected from thegroup consisting of a tumor-specific antigen, a major histocompatabilitycomplex antigen and a costimulatory molecule.
 9. An MP according toclaim 8 , wherein said costimulatory molecule is B7. 1 or B7.2.
 10. AnMP according to claim 5 , wherein said immunostimulator is a lymphokine.11. An MP according to claim 10 , wherein said lymphokine is IL-2. 12.An MP according to claim 5 , wherein said immunostimulator is aninterferon.
 13. An MP according to claim 12 , wherein said interferon isIFN-γ.
 14. An MP according to claim 5 , wherein said immunostimulator isa cytokine.
 15. An MP according to claim 14 , wherein said cytokine isGM-CSF or M-CSF.
 16. An MP according to claim 5 , wherein saidimmunostimulator is an adjuvant.
 17. An MP according to claim 16 ,wherein said adjuvant is selected from the group consisting ofmonophosphoryl lipid A, lipid A and muramyl dipeptide (MDP) lipidconjugate.
 18. An MP according to claim 5 , wherein said lipid is asaturated or unsaturated phospholipid or a glycolipid.
 19. A MPaccording to claim 18 , wherein said lipid is selected from the groupconsisting of 1,2-dimyristoylphosphatidylcholine,1,2-dipalmitoylphosphatidylcholine, 1,2-dimyristoylphosphatidylglycerol,cholesterol and combinations thereof.
 20. An MP according to claim 5 ,wherein said lipid forms a membrane within which said integral membraneis patched.
 21. An MP according to claim 5 , wherein said lipid formspatches within said integral membrane.